Pulmonary insufficiency associated with immaturity is one of the most common life-threatening hurdles that confronts the premature newborn baby. The newborn's rib cage is soft and buckles easily during spontaneous respiration. Underdevelopment of the intercostal muscles contributes to the chest's deformability. In premature infants below 30 weeks gestation, thoracic wall elastic recoil is almost non-existent so that the resting volume of the lungs is very close to or below their collapsed volume. Also, the compliant chest wall tends to collapse as the diaphragm descends, resulting in a diminished tidal volume. As a result, most premature infants require assisted ventilation and/or continuous distending pressure (CDP).
Continuous positive airway pressure (CPAP) is widely established as an effective method for preventing lung wall collapse, chest wall distortion and for increasing oxygenation. Currently, CPAP is used almost exclusively in preference to continuous negative distending pressure. CPAP, however, is potentially hazardous. It is usually administered by nasal prongs, but has major limitations and serious side effects. These include: nasal trauma; difficulty in obtaining a good fit in very small infants; high gas flows which cause cooling, drying and obstruction of the nasal passages; during periods of crying and mouth opening, especially with high flows, there is a loss of pressure and the infant inhales room air; and frequent dislodgement makes nursing difficult, especially when associated with repeated bouts of desaturation. Fluctuating saturation may increase the risk of retinopathy. Perhaps more serious are the circulatory disturbances: decreased venous return to the heart; diminished cardiac output; and increased intra-cranial hemorrhage.
Negative pressure applied intermittently around the chest has been used for more than a 100 years as a way of assisting ventilation in patients with respiratory failure. The iron lung is perhaps one of the best recognized negative pressure ventilators. Continuous negative distending pressure (CNP) is used to manage a number of specific conditions that produce respiratory failure in neonates and older infants. Negative distending pressure is highly effective and does not have many of the side effects of CPAP. Among its benefits with patients with respiratory disease syndrome are an increase in resting volume of the lung and arterial oxygen tension. There is also no need for an airway or nasal prongs. As opposed to positive distending pressure, CNP produces a decrease in intrathoracic and right atrial pressures, favoring venous return to the heart from parts of the body that are not exposed to the negative pressure. CNP further increases lung lymph flow and lung albumen transport. CNP also avoids the increases in pulmonary vascular resistance and pulmonary artery pressure that are observed with positive airway pressure. Recently, CNP has been re-introduced to treat infants with various pathological conditions.
While improvements have been made in the design of devices for generating extra-thoracic negative pressure, the devices are still difficult to attach to small newborns. Current designs consist of a cuirass or chamber and use vacuum around the chest or lower body to generate negative pressure. These devices require some form of electrical power supply, are relatively expensive and are cumbersome. Technical difficulties are associated with temperature control, neck seals obstructing venous return, leaks around the seals and limited patient access. These devices require considerable training and experience to operate and the technical problems make nursing difficult and frustrating. This limits the use of a potentially life saving treatment modality.
Providing and caring for ever-diminishing-size preterm infants is an everyday challenge in the neonatal intensive care setting.
Accordingly, it is an object of this invention to provide a chest brace which enables continuous negative distending intra-thoracic pressure to be applied to a patient.
It is a further object of this invention to provide a chest brace which reduces buckling (retraction) of a patient's chest wall during breathing.
It is another object of this invention, to provide a chest brace which provides continuous negative pressure on the patient's chest cavity without requiring vacuum seals.
It is yet another object of this invention to provide an improved continuous negative pressure chest brace which is particularly adapted for use with premature newborn babies.
It is still another object of this invention to provide an improved chest brace that is simple to attach, inexpensive and does not require electrical power.
It is still a further object of this invention to provide an improved chest brace which is adapted to provide intermittent negative pressure ventilation for a patient without a need for endotracheal intubation.